Recently, products that adopts solid-state light sources, such as an LED (light-emitting diode) and an LD (laser diode), as light sources used in projectors for presentation or for digital cinema have been increasingly used instead of mercury lamps, xenon lamps, and the like used in related art. The fixed light sources such as LEDs have advantages such as having long lifetime, no replacement of lamps, which is necessary in related art, and lighting-up immediately after power-on.
Such a projector includes a type in which a solid-state light source is directly used as a light source. On the other hand, there is another type in which a light emitter such as a phosphor, which is excited by excitation light to emit light, is used as a light source. In this case, the solid-state light source is used as an excitation light source that outputs excitation light.
For example, in a light source device described in Patent Document 1, blue light output from first and second solid-state light source groups is collected by a light collecting optical system and applied to a phosphor generation unit. In the phosphor generation unit, with the blue light as excitation light, a phosphor containing red light and green light is generated. Thus, white light containing the blue light, the red light, and the green light is output from the phosphor generation unit (see FIGS. 1 and 2 etc. of Patent Document 1).
Patent Document 1: Japanese Patent Application Laid-open No. 2012-118302